1. Field of the Invention
This invention relates to a cell voltage measuring device for a fuel cell, which measures voltage by terminals contacting separators in the fuel cell.
2. Background Art
A solid polymer electrolyte fuel cell unit (hereinafter simply referred to as a fuel cell unit) comprises: a solid polymer electrolyte membrane as a cation-exchange membrane; an anode electrode and a cathode electrode which together hold the solid polymer electrolyte membrane therebetween; and a pair of separators which hold the anode and cathode electrodes. A plurality of fuel cell units are stacked together to form a fuel cell stack in actual use.
In such a fuel cell stack, as a device which enables monitoring whether or not each fuel cell unit is operating normally, a cell voltage measuring device is known from, for example, Japanese Unexamined Patent Application, First Publication No. Hei 9-283166, in which voltage generated by the fuel cell unit (hereinafter simply referred to as cell voltage) is measured by a terminal inserted into a circular hole formed in the separator.
As another type of device, a cell voltage measuring device in which cell voltage is measured by an elastic terminal which is pressed against the bottom of a groove formed in the separator, is also known.
However, in the former type of cell voltage measuring device, it is difficult to form the circular hole because the separator is thin when the separator is made, for example, by press-forming a thin metal plate.
On the other hand, in the latter type of cell voltage measuring device, high reliability in measuring cell voltage can be obtained because the terminal is pressed against the bottom of the groove and a stable contact resistance can be realized; however, a further improvement is desired because the terminal may come out of the groove due to vibration or the like, depending on the dimensional relationship between the diameter of the terminal and the size of the groove.